Four Channels

The gut and brain talk over more than one line. There are four:

• Neural - the vagus nerve relays signals between gut and brain within seconds
• Hormonal - gut cells release hormones that shape your appetite, mood, and stress response
• Immune - inflammation in the gut sends alarm signals that can dull mood and thinking
• Microbial - gut bacteria make chemical messengers and help regulate serotonin production in gut-lining cells

Here is the eerie part. When researchers transplanted gut bacteria from anxious mice into calm mice, the calm mice turned anxious. The microbes, not the mice, were steering the behavior.